015-016 类中方法中的this，解决类中this指向问题

类中方法中的this!DOCTYPE html html langen head meta charsetUTF-8 meta http-equivX-UA-Compatible contentIEedge meta nameviewport contentwidthdevice-width, initial-scale1.0 titleDocument/title /head body script typetext/javascript class Person { constructor(name, age) { this.name name this.age age } study() { //study方法放在了哪里 —— 类的原型对象上供实例使用 //通过Person实例调用study时study中的this就是Person实例 console.log(this); } } const p1 new Person(tom, 18) p1.study() //通过实例调用study方法 const x p1.study x() //undefined /script /body /html解决类中this指向问题!DOCTYPE html html langen head meta charsetUTF-8 meta http-equivX-UA-Compatible contentIEedge meta nameviewport contentwidthdevice-width, initial-scale1.0 titleDocument/title /head body div idtest/div script typetext/javascript src../js/react.development.js/script script typetext/javascript src../js/react-dom.development.js/script script typetext/javascript src../js/babel.min.js/script script typetext/babel //1.创建组件 class Weather extends React.Component { constructor(props) { super(props) //initialize state this.state { isHot: true } //解决changeWeather中this指向问题 this.changeWeather this.changeWeather.bind(this) //bind()返回了一个新函数并且把this修改为括号中的内容 } render() { //read state const { isHot } this.state //解构赋值 return h2 onClick{this.changeWeather}今天天气很{isHot ? 炎热 : 凉爽}/h2 } changeWeather() { //changeWeather放在哪里 —— Weather的原型对象上供实例使用 //由于changeWeather是作为onClick的回调所以不是通过实例调用的是直接调用 //类中的方法默认开启了局部的严格模式所以changeWeather中的this为undefined console.log(this) } } //2.渲染组件到页面 ReactDOM.render(Weather /, document.getElementById(test)) /script /body /html